Dry kiln



y 3 G. H. WOOLHOUSE DRY KILN Fil ed June 1, 1931 2 Sheets-Sheet 1 A Geargefilfioo/Zzouse G. H. WOOLHOUSE DRY KILN July 25, 1933.

Filed June 1, 1931 2 Sheets-Sheet 2 92 50 Geargefi [1100112011512 Patented July 25, 1933 "UNITED STATES PATENT orries GEORGE H. WOOLI-IOUSE, F TACOMA, WASHINGTON, AssIe on or ONE-HALF To 1 1. BOWERS, or SEATTLE, WASHINGTQN DRY KILN Application filed June 1, 1931. Serial No. 541,238.

My invention relates to dry kilns of the type employed for drying lumber.

Various problems are met with in the kiln-drying of lumber. The air must be 5 kept moving continuously and at a substantially constant velocity throughv the lumber. The volume supplied depends upona number of factors, among them the leakage into or from the kiln through" cracks and crevices and around doors, the condition of the lumber, the particular wood, and the size of the pieces. At certain times there must be supplied a greater volume of air in a given period than at other times.v It is also desirable at times to supply fresh air from outside to the air within the kiln, to replace that lost through the vents or to cause movement of the air from within the kiln through the vents. Such kilns operate for considerable periods of time and it is of course desirable to cause and keep up movement of air with the least power, and hence, it is necessary to reduce to the minimum power losses through air frictional losses in the fans employed, and through changes in direction of the airs movement. It is also desirable to prevent end drift of the air, so that it will circulate rather in a straight-through circle, that is to say, in transverse planes which are substantially at right angles to the length of the kiln.

It is also essential that the direction'of movement of the air be reversed from time to time, so that the lumber will dry evenly in the pile, and so that one side of the pile will not become dry more quickly or to a greater degree than the lumber at the opposite side of the pile. It is, of course, desirable to eliminate duplication of motors and fans to cause this reversal, and to employ the same fans for advancing the air in one direction as in the opposite direction.

Constant speed motors are most desirable for operations of this type where the mechanism operates continuously for considerable periods, and it is also desirable to simplify the driving and controlling meansin such a kiln.

My invention is directed to the objec ndicated above, enabling movement of the air in one direction or in the other-with a reversible fan, several such fans being dis tributed along the length of the kiln, and the conduits being so. arranged as to sub- *15 stantially eliminate end drift of the air and to keep it moving. always in the given direction in a substantially plane circular path, the fan operatingat constant speed and the volume beingcontrolled, and con in trolled as regards the relation of one fan to the other, by simple means, and fresh air being supplied asnecessary. V

' The principles of my invention will be best understood by reference to the accomt5 panying drawings, wherein my invention'is shown in a form which 'at present is preferred by me, the same embodying the principles of my invention, and in which Figure lis a transverse section through a kiln with lumber therein in process of drying, Figure 2 is a longitudinal. section through the same, substantially on the axis of the fans, and Figure 3 is a horizontal section'substantially along the line 3-3 of Figure 2.

The kiln may be constructed in various ways, and I have illustrated a housing which I designate generally by the numeral 7. This is of considerable length, and defines the drying chamber 7O. Roof vents 71 may be supplied as is customary or desirable, and fresh air is supplied to fans, which 'will be described later, through a conduit 9, which extends the length of the kiln, and which may be outside of the drying chamber 70 or 5 inside of the same, as shown herein.

, Within the drying chamber a support is arranged above its bottom vfor a pile of. lumber, illustrated at L, the piecesbeing. piled according to any approved method to allow for circulation of air'around and being from the center of rotation outwardly,100

and the several fans may for convenience be axially aligned and supported upon a common drive shaft 2. Each fan is encased within a casing 11, which partially encloses it; preferably about the upper three-fifths of the periphery-that is to say, somewhat more than a half of the fan, is enclosed, leaving the lower portion, say about twofifths of the total periphery, exposed. T he casing 11 fits closely about the fan, so that the air will not move round about through the casing. but this will in effect be a dead air space, holding the air within the pockets between the radial vanes 10.

Extending in a general outward and upward direction from the fan casing 1.1 at each'side are conduits 23. Preferably these are flared outwardly from the fan, and they extend to the sides of the drying chamber 70; They are of substantially like cross sectional area throughout, so that the effect of flaring will be merely to cause longitudinal CllStIilJHtiOllOf the air passing through the fan. One of these conduits is a suction conduit andthe other is a discharge conduit. or the conditionmay be reversed, depending upon the direction of rotation of the fan. These conduits 8, with the fan housing 11, complete astraight thrOugh passage. with an easy angle downward from one w: ll of thedrying cham'berand upward alone; the opposite side wall, sothatthe air is led in a straight-through passage without abrupt change of direction; and without any right angle turns in the fan itself. The fan acts as'a' paddle wheel to keep the air moving, and the blades arespaced from the bottom '30 'of the aircondu-it,

To heat the air and to maintain its temperature, various means maybe employed. As shown herein. heating'coils 13 are installed at the outer end of each of the conduits 3, steam being supplied through the main 14. Condensation is removed through the conduits 15. The presence of the heating coils 13 in the ends of the conduits-3 serves to bafile'theair to some extent, and to'distribute'it' evenly lengthwise so that the volume emitted from the extreme end of a conduit 8 is substantially the same as that emitted through the center thereof. In consequence of this, and because the conduits 3 are placed closely adjacent one another, the volume of air and its velocity is substantially the same at any given instant throughout the length of the kiln. In consequence, be cause of the lack of variation in volume or velocity lengthwise of the kiln, there no tendency to endwise drift. A battle or ourtain would naturally be employed at 16, lying close to the top of the pile of lumber L, to prevent circulation over the top of the pile, and to force the air to pass through the'lumber. No other baffles need be employedhen it is desired to supply a greater volume of air, this can be done without causing an increase in the speed of rotation of the fan 1. To this end I provide a bypass conduit d, extending from the conduit 3 at one side of a fan to the opposite conduit 3 at the other side. Between the ends of the by-pass conduit a communication is established with one side of the fan casing 11 through an a )erture ll. At the 'unction with each of the conduits 3 dampers are provided, and these are designated 42 and 43 to distinguish them, though they are, or may be, of like construction and similarly controlled and operated. dampers is pivoted upon a rod 40 to control its aperture, which in the one instance is designated i -l. and in the other instance L5, to distinguish them. The dampers are swung by such means as the rods 46 and d7, controlling arms 48 upon the ends of the rods 40. The rodselG and -17 may extend the entire lengthof the kiln, and may control the like dampers for each of the fans.

since it may be necessary because of leakage through doors and the like, at the end of the kiln, for instance, to supply a greater volume at the end than in the center,.the setting of the individual arms i8, relative to the rods or' li', may vary with the dampers for each fan, so that a given move ment of the controlling rod, 46 or 4:7, will effect a different amount of movement of the several dampers.

So long as the dampers i2 and i3 are closed it is evident that no air will pass through the by-pass conduits l or enter at the aperture .411. I have discovered, however, that if one of these dampers is open (that one which communicates with the conduit 3 which at the moment is thesuction conduit), air will be drawn through this conduit in greater volume, and a certain n'opOrtionc-fit, depending upon the amount of opening of the damper, will enter through the aperture 41, being drawn in by the suction created by the fan in passing this aperture, and the fan, without increase of speed, will commence to deliver a greater volume of air. lVith an aperture suliiciently large, the volume handled can be increased by 50%, in-ovidcd the fan is properly designed. Naturally, the power re quired increases at such times, but the motor 20, which may be a constant speed reversiblc motor, would be so designed as to carry such increased load.

At times it will be desirable to supply additional fresh air, and for this purpose I have shown fresh air passages 91 connecting the fresh air conduit 9 with each of the fan casings. Such a conduit preferably is somewhatsmaller than the by-pass conduit 4:, and communicates with the opposite side of the fan casing through an aperture 93.

Each of these 0 it'll There need be no damper control for the individual fresh air passages, but all may be controlled by opening the door 92 at the entrance to the fresh air .conduit Elmore or less, as may-be required.

As in the case ofthe by-pass conduit, air will be drawn into the fan casing through the aperture 92 whenever fresh. air isadmitted into the fresh air conduit 9, and the suction of the fan in passing the aperture 92 will draw it in and cause it'to be discharged with the circulating air .into the drying chamber 7,0, thereby increasing the total volume discharged. As much as 20% additional volume can be supplied in this way, with the design illustrated. The

amount of fresh air may be regulated, as

description in detail is necessary. .It will beevident that various changes may be made in the form, proportion and arrangement of the several parts constituting the invention, without departing from the spirit thereof, as has been herein disclosed, and as will be more particularly pointed out in the following claims.

What I claim as my invention is:

1. A lumber dry kiln comprising a housing defining a drying chamber of considerable length, a plurality of fans having radition and discharge, extending 'ating vanes, and spaced at intervals along the length of the chamber, a fan easing partially enclosing each fan, conduits, for sucfrom the exposed portion of each fan to each side of the drying chamber, and constituting, with the fan casing, a straight-through passage for air, reversible means to rotate the fans, a fresh air supply conduit, an individual connection from the same to each fan casing, and means to control admission of fresh air to the fan casings.

2. A lumber dry kiln comprising a housing defining a drying chamber of considerable length, a plurality of fans having radi-' ating vanes, and spaced at intervals along the length of the chamber,a fan casing partially enclosing each fan, conduits, for suction and discharge, extending from the exposed portion of each fan to each side of the drying chamber, and constituting, with the fan casing, a straight-through passage for air, reversible means to rotate the fans, a fresh air supply conduit, an individual connection from the same to each fan casing,-

and a single door controlling admission of fresh air to the fresh alr supply conduit.

3. A lumber dry kiln comprisii'ig a housa 2'- .ing defining a drying chamber of considerable length, a plurality of fans having radiating vanes, and spaced at intervals along the length of the chamber, a fan casing partially enclosing each fan, conduits, for suetion and discharge, extending from the exposed portion of each fanto each side of the drying chamber, and constituting, with the fan casing, a straight-through passage for air, a bypass conduit from the suction and discharge conduits of each fan to the fan casing, dampers controlling the'passage of airthrough the individual by-pass conduits, acommon operating means for the several dampers, and reversible means to rotate the several fans.

l. A lumber dry kiln comprising a housing defining a drying chamber of'considerable length, a plurality of fans having radi ating vanes, and spaced atintervals along,

the length of the chambera fan casing partially encloslng each fan, conduits, for suction and discharge, extending from the exposed portion of each fan to each side of the drying chamber, and constituting, with the fan casin a straight-through passage for air, a by-pass conduit from the suction and discharge conduits of each fan to the fan casing, dampers controlling the passage of air throughthe individual by-pass conduits, a common operating means for the several dampers, means tovary the degree of opening of ,lIlCllVldHal dampers relative to the others caused by said common operating means, and reversible means to retate the several fans.

5. In a lumber dry kiln, the combination comprising a housing defining a drying chamber, a fan having its axis parallel to the length of the chamber, and having vanes radlally disposed, a fan casing partially enclosing the fan, conduits, for suction and discharge, extending from the exposed portion of the fan to each side of the drying chamber, and constituting with the fan casing, a straight-through passage for air, a by-pass conduit connecting the suction con duit with the side of the fan casing, means to control or prevent passage of air through said by-pass, and a constant speed motorfor rotating the fan. I

6. In a lumber dry kiln, the combination including a housing defining a drying chamber, a fan having its axis parallel to the length of the chamber, and having vanes radially disposed, a fan casing partially enclosing the fan, like conduits for suction anddischarge extending from the exposed portion of the fan to each side ofthe drying chamber, and flared longitudinally outwardly of the fan, but of like capacity throughout, said conduits constituting, with the fan casing, a straight-through passage for air, a by-pass conduit extending from the suction to the discharge conduit, and communicating between its ends With the side of the "fan casing, damper means to control or prevent admission of air through said by-pass to the 'fan casing, and reversible means to rotate the fan.

7,111 a lumber dry kiln, the combination comprising a housing defining a drying chamber, a fan having its axis parallel to the length of the chamber, and having vanes radially disposed, a fan casing partially enclosing the fan, conduits, for suction. and discharge, extending from the exposed portion of the fan to each side of the drying chamber, and constituting, With the fan casing, a straight-through passage for air, a by-pass conduit connecting the suction conduit with the side of the fan casing, means to control or prevent passage of air through said by-pass, a passage to introduce fresh air to the fan casing, means to control or prevent such introduction of fresh air, and means to rotate the fan.

8. In a lumber dry kiln, the combination including a housing defining a drying chamber, a fan having its axis parallel to the length of the chamber, and having vanes radially disposed, a fan casing partially enclosing the fan, like conduits i'or suction and discharge extending from the exposed portion of the fan to each side of the drying chamber, and flared longitudinally outwardly of the fan, but of like capacity throughout, said conduits constituting, With the fan casing, a straight-through passage for air, a bypass conduit extending from the suction to the discharge conduit, and communicating between its ends With the side of the fan casing, damper means to control or prevent admission of air through said by-pass to the fan casing, a passage to introduce fresh air to the side of the fan casing opposite the by-pass, means to control or prevent such introduction of fresh air, and reversible means, to rotate the fan.

GEORGE H. WOOLHOUSE. 

